ACE Weekly 08/23/2011 - 08/29/2011

All ACE spacecraft subsystems are performing nominally.

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Orbit/Attitude:

No maneuvers were completed this week.  The next attitude maneuver is
scheduled for Tuesday 08/30/2011.

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OCRs:

DOY 238 (08/26/2011)  1520-1527z  SWICS
Three emergency commands from the SWICS safing procedure were executed
to reduce the voltages on the instrument.  A large background had
started around Tuesday 08/23/2011 (DOY 235) and the commands were sent
to prevent possible damage to the instrument. The instrument team is
analyzing their data to decide further action. (AR#S11-0002).


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Activities:

Data Capture:  99.98%  DOY 233-240 2011
There were 146 seconds of data missing on DOY 238 2011 from 0518-0526z.
This was due to a combination of factors including SSRA being stuck in
playback, the SSR restarting playback while DSN was first acquiring the
high data-rate and no SSR redumps performed when we're behind in the SSR
playback.

	2     05:18:02-05:18:03     4     05:25:17-05:25:20
	59    05:23:25-05:24:23     7     05:25:23-05:25:29
	8     05:24:26-05:24:33     3     05:25:32-05:25:34
	4     05:24:35-05:24:38     36    05:25:44-05:26:19
	23    05:24:50-05:25:12

DSS-54 has had problems for the past week.  ACE released time to help
other missions impacted by the DSS-54 outage.
Monday 08/22/2011 (DOY 234) pass shortened 1 hour for SOHO
Friday 08/26/2011 (DOY 238) pass shortened 2 hours 5 minutes for WIND

The GRAIL mission is expected to launch 09/08/2011.  ACE has reduced DSN
antenna time during September.  The current schedule has ACE losing ~15%
data over 3 weeks in September.  The data loss will be greater if there
are problems with any of the passes.

NOAA Space Weather Prediction Center (SWPC) uses 3 main sites to track
ACE in-between DSN passes: NICT/Japan, DLR/Germany and
WCDA/Wallops,Virginia.  WCDA (Wallops) shut down over the weekend due to
Hurricane Irene.  NOAA acquired AFSCN time on Sunday 08/28/2011 from
13:50-17:15z and 2045-2145z.  This was the first operational use of the
new VAFB SCD and network route via the MMOC.  The data flow was
successful after NOAA SWPC performed some investigation.  NOAA's
processing of SWEPAM data stopped during this time, but was restored at
1600z Monday 08/29/2011.

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Anomalies:

DOY 238  08/26/2011  S-ACE-0542  S10-0008  SSR A Stuck in Playback
When the SSR playback is longer than the pass, the SSR is commanded to
idle before switching to the low-rate (RTSW) data format.  The pass was
shortened for WIND and the SSR was not commanded to idle before the new
EOT.
Impact:  The ground procedures are designed to handle this contingency.
However, 146 seconds of data was lost because redumps were not
performed.  This has occurred 6 other times in the past.

DOY 238  08/26/2011 S-ACE-0543  S11-0002  SWICS problems
The instrument team found an abnormally large and possibly growing
background starting around Tuesday 08/23/2011 (DOY 235).  The trigger
rate on SWICS started increasing to 10 times normal.  There was concern
that the instrument might be degraded, so the instrument was commanded
to lower the MCP detector high voltage and the post-acceleration voltage
on Friday 08/26/2011 (DOY 238).
Impact:  The instrument team is analyzing their data to decide further
action.